Have requests for views that use 'stale=ok' return whats in the index
immediately, but still kickoff background indexing process.
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Key: COUCHDB-532
URL: https://issues.apache.org/jira/browse/COUCHDB-532
Project: CouchDB
Issue Type: Improvement
Components: Database Core
Environment: All
Reporter: Glenn Rempe
Currently a common use case for querying indexes from external applications is
to pass in the optional parameter 'stale=ok' which instructs the view to return
what is has in its index immediately without waiting for the index to first
catch up.
This is a *very* important feature as it allows applications to eliminate the
poor user experience of potential HTTP client timeouts or long'ish waits for a
query to return while the index is updated.
However, applications that make extensive (or in my case exlusive) use of this
feature are now essentially *required* to build some kind of script which will
do the indexing in the background since no user requests will *ever* initiate
indexing. This would be for example a cron script that makes an HTTP call to
the view every N hours. This becomes an operational issue as you now have to
write, maintain and schedule an external script which calls each view in each
of your DBs periodically.
I propose to the team, after some discussion with Paul Joseph Davis, that view
requests with the 'stale=ok' param continue to return results in the as-is
index to users immediately, but *also* kick off the background indexing
process. This would have the effect of removing the need for any external
maintenance scripts (aside from DB/View compaction which is a related but
separate issue).
In some use cases it might be true that indexing *must* occur outside of
'normal business hours' due to processing load. If this is a requirement the
behavior of view indexing on 'stale' requests could be configurable (e.g. as a
boolean to always/never do this additional background indexing, or force BG
indexing every N requests/minutes using 'stale').
Cheers.
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